Torches which burn liquified petroleum gas and valves for regulating the flow of said gas to the torch are well-known in the art. Examples of such torches and valves are disclosed in U.S. Pat. Nos. 3,736,093; 3,475,110; 3,978,880; 3,865,137; and 3,891,195.
The most commonly used torches utilize fuel gas available from a pressurized container wherein the fuel gas is in liquid state. Fuel is vaporized in the container and exits the container through an outlet valve. Then, the fuel flows into the torch through a control valve or regulator. The amount of fuel flowing into the torch depends, not only on the flow passage opening provided by the valve, but also, on the internal pressure of the container. That pressure is a direct function of the ambient temperature. As a result, in the absence of some means to regulate the flow of fuel, large swings in ambient temperature greatly affect the amount of fuel flowing into the torch which is designed to operate at room temperature. When such a torch is operating under sub-freezing temperatures, the flame of the torch becomes very small and essentially useless. Alternatively, when the ambient temperature is very high, i.e. when the torch is used in the summer or in a hot environment, the flame becomes so large so as to be unmanageable.
In the past, torches have been developed to overcome this problem by utilizing different orifice sizes for different ambient temperatures or by utilizing diaphragms which are exposed to and respond to fuel pressure variations. Examples of valves utilizing diaphragms to maintain a constant flow when the internal pressure of the fuel source varies are disclosed in U.S. Pat. Nos. 3,475,110; 3,736,093; 3,978,880; and 3,865,137.
Another problem encountered in torches is that, although fuel is primarily vaporized in the fuel source, oftentimes, fuel exits the fuel source and enters the torch in the liquid phase. That problem is more common in portable torches which are sometimes turned upside down in order to direct the flames against a horizontal surface. When fuel enters the torch in the liquid phase, it produces a large yellow flame rather than the more desirable blue flame because the air/fuel mixture is not sufficient for such flame. In order to solve that problem, the prior art has attempted to increase the number of pressure drop points in the flow passage between the pressurized fuel source and the torch to increase the number of vaporization stages thereby decreasing the likelihood of liquid fuel entering the torch.
One disadvantage of the prior art torches that have attempted to solve the above problems is that, due to the inclusion of diaphragms and multi-stage pressure drop points, they are complex, bulky, expensive and, oftentimes, subject to failure due to such complexity. This disadvantage is overcome by the present invention which discloses a simple valve for regulating the flow of fuel from a pressurized fuel source to a torch which is simple, reliable, and inexpensive and which may be utilized in both cold or hot environments to give a desirable torch flame. The valve adjusts the flow of fuel passing therethrough automatically in response to the pressure in the fuel source and in the valve downstream over a wide range of operating temperatures and requires minimum manual adjustment during its operation. Furthermore, the valve vaporizes liquid fuel that may flow from the fuel source to the valve.
These and other objects and advantages of the present invention will become readily apparent from the following description.